The present invention relates to electrical apparatuses, etc. provided with a battery that charges, then discharges. More particularly, the present invention relates to electrical apparatuses, etc. intended for improving usability of the battery.
In addition to commercial power sources that supply power directly, batteries that can be reused through charging/discharging (power accumulators, secondary batteries, and primary batteries) are used to power information terminals such as by laptop personal computers (PCs), personal devices such as as a PDA (Personal Digital Assistant), and various kinds of electrical apparatus such as portable audio devices, video cameras, etc. Nickel hydrogen batteries (NiMH batteries) and nickel cadmium batteries (Ni—Cd batteries) are comparatively large in capacity and low in price are employed in such applications. There are also other types of batteries such as lithium ion batteries which are higher in energy density per unit weight than nickel cadmium batteries, as well as lithium polymer batteries which use solid polymer without using liquid electrolyte.
The nickel hydrogen batteries and the nickel cadmium batteries, however, are degraded in charging capacity when they are frequently charged half-way and then discharged incompletely. As a result, the so-called “memory effect” occurs. The “memory effect” is a phenomenon wherein continuous operating time of the battery is reduced. In addition, for an intelligent battery provided with an internal CPU, when half-way charging and incomplete discharging are repeated, errors are accumulated in such measured values as the residual capacity of the battery, thereby making correct measurement difficult. In recent years, however, there have appeared a device that can eliminate the “memory effect” from intelligent batteries with a refreshing function that discharges the battery completely even when the subject apparatus is connected to an AC adapter (power source). A technique that refreshes batteries to eliminate errors from measured values is now under examination for intelligent batteries.
Furthermore, “peak shifting” has also been required in recent years to reduce the peak power consumption during a time in which power consumption rises significantly, for example, during a summer afternoon in which power consumption increases due to the operation of air conditioners. When electrical apparatus are configured so as to be powered only from batteries when power from commercial sources via an AC adapter stops in such a much power consuming time zone, such the peak time power consumption (in time zones of extremely high power demand) will be more reduced.
However, the power line from the commercial power source is disconnected completely while the battery is refreshed and the peak-shifting is done with the above-described technique. In the case where the user disconnects the battery by mistake in such a state, no power is supplied to the computer system, thereby the system will be shut down. Especially, if the computer system is shut down suddenly in such a computer as a lap-top PC, for example, the current task cannot be recovered and the data in the processing will be lost. In addition, the hardware in the computer system might be damaged.
Under such circumstances, it is an object of the present invention to prevent an electrical apparatus connected to a battery from shut-down even when the battery is disconnected while the power line from the physically connected commercial power source is disconnected (circuit disconnection) and the battery powers the body.